This invention relates generally to switch actuator mechanisms and more particularly, it relates to an improved electrical switch actuator mechanism which provides tactile and/or audible feedback to a user. The present invention has particular applications for use in keyboard assemblies having multiple key-switches to signal utilization electronic devices such as Laptop personal computers, typewriters, pocket calculators, telephones and the like.
Generally, there are known to exist in the prior art various manually activated switching apparatus for engaging electrical contacts to complete an electrical conduction path. Some of the prior art designs utilize a compression column spring in conjunction with a rocker actuator. For example, in U.S. Pat. No. 4,118,611 issued on Oct. 3, 1978, to Richard H. Harris, there is shown and described a pivoting switch actuator using a buckling compression spring to move the actuator in response to depressions of a key in which the actuator causes closing and opening of a switch through changing the capacitance between contacts with which the actuator cooperates.
Also, there is taught in U.S. Pat. No. 4,528,431 issued on July 9, 1985, to Edwin T. Coleman III, a buckling spring which extends between a key and a pivoting rocking actuator for causing closure of the contact switch of a membrane contact switch assembly when the key is depressed. In particular, the pivoting rocking actuator has a first bottom surface, which comprises two spaced portions, resting on an upper surface of the membrane contact switch assembly when the actuator is in its rest position. When the key is depressed, the spring buckles in a selected direction to cause initial pivoting of the actuator about a forward edge of each of the spaced portions. This causes a curved bottom surface of the actuator to rotate about a pivot point on the bottom curved surface so as to close the contact switch. When the key is released, the spring unbuckles at a slower rate than its compression so that the actuator initially further rotates in the same direction in which it is rotated during depression of the key prior to rotation in the opposite direction to return the actuator to its initial rest position.
In U.S. Pat. No. 4,479,040 issued on Oct. 23, 1984, to Ronald S. Denley et al., there is disclosed a switch having tactile feedback which includes a housing, a set of electrical contacts, a reciprocative plunger, an actuator, and a coupler. A first spring is located between the plunger and the actuator for biasing them apart. The coupler includes a blocking tang which engages the actuator during a first portion of the plunger stroke to prevent movement of the actuator. A second spring is located between the coupler and the housing to bias the coupler upwardly. After a predetermined amount of plunger travel, a trip mechanism separates the coupler from the plunger with the resulting decrease in resistance to the plunger stroke so as to provide the tactile feedback to the operator. Simultaneously, the blocking tang disengages the actuator so that the first spring is able to cause the actuator to close the switch contacts.
Still other prior art key-switch actuator designs utilize a dome-type actuator made of silicone rubber for opening and closing switch contacts to provide for electrical connection. A search conducted by applicant and directed to the subject matter of this application uncovered the following additional patents: U.S. Pat. Nos. 4,002,871; 4,123,627; 4,245,138; 4,433,224; 4,405,845; and 4,528,428. However, these latter patents are considered to be only of general interest.
Therefore, these prior art switch actuator mechanisms have a significant drawback in that the materials used in manufacturing the buckling springs and the rubber dome-type actuators have inherent problems in reliability and in quality control. Specifically, during mass production it is difficult and costly to maintain these parts within the required tolerance necessary for proper switch operation. Further, it has been encountered that the prior art switch actuator mechanisms utilizing a buckling spring have corrosion problems in certain environments, thereby limiting its useful life. Additionally, these prior art devices have disadvantages due to the use of a large number of parts and thus resulting in increased manufacturing and assembly costs.
Accordingly, it would be desirable to provide an improved electrical switch actuator mechanism which is more reliable and accurate in operation and can be manufactured more economically without the need of high tolerances as required in the prior art. Further, it would be expedient to provide an improved electrical switch actuator mechanism which is constructed of a relatively few number of components so as to facilitate easy and quick assembly.